package queuecode;

/**
 * @author noob
 * @version 1.0
 * @date 2021/3/14 14:24
 */
public class LoopQueue<E> implements Queue<E> {


    private E[] data;
    private int front,tail;
    private int size;

    public LoopQueue(int capacity){
        data = (E[])new Object[capacity + 1];
        front = 0;
        tail = 0;
        size = 0;
    }

    public LoopQueue() {
        this(10);
    }

    public int getCapacity(){
        return data.length - 1;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return front == tail;
    }

    @Override
    public void enqueue(E e) {
        if((tail + 1)%data.length == front){//判断队列是否已满
            resize(getCapacity() * 2);
        }
        data[tail] = e;
        tail = (tail + 1) % data.length;
        size++;
    }

    private void resize(int newCapacity) {
        E[] newData = (E[])new Object[newCapacity + 1];
        for (int i = 0; i < size; i++) {
            newData[i] = data[ (i+ front) % data.length];
        }
        data = newData;
        front = 0;
        tail = size;
    }

    @Override
    public E dequeue() {
        if(isEmpty()){
            throw  new IllegalArgumentException("队列为null，不能出队");
        }
        E oldE = data[front];
        data[front] = null;
        front = (front+ 1) % data.length;
        size--;

        if((size == getCapacity() / 4) && (getCapacity() / 2 !=0) ){
            resize(getCapacity()/ 2);
        }
        return oldE;
    }

    @Override
    public E getFront() {
        if(isEmpty()){
            throw  new IllegalArgumentException("队列为null");
        }
        return data[front];
    }

    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        res.append(String.format("LoopQueue: size = %d, capacity = %d\n",size,getCapacity()));
        res.append("front [");
        for (int i = 0; i < size; i++) {
            res.append(data[i]);
            if ( (i+1) % data.length != tail){
                res.append(", ");
            }
        }
        res.append("] tail");
        return res.toString();
    }





}
